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<TITLE>Re: [mapguide-users] Guestion about speedup mapguide,diferent domainname to mapagent.fcgi.</TITLE>
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<DIV>Yes, the problem of the tiles not necessarily being on the same machine as
the web server is one of the limitations/assumptions that I had in mind also.
But then I decided that this can be worked around by using a file
system mount from the web server to the server where the tiles are. I've
seen a similar thing done on Linux/Apache, not sure if Windows
could handle such a setup.</DIV>
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<DIV>Traian</DIV>
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<DIV><FONT size=2>-----Original Message----- <BR><B>From:</B>
mapguide-users-bounces@lists.osgeo.org on behalf of Paul Spencer
<BR><B>Sent:</B> Wed 2/28/2007 8:00 PM <BR><B>To:</B> MapGuide Users Mail List
<BR><B>Cc:</B> <BR><B>Subject:</B> Re: [mapguide-users] Guestion about speedup
mapguide,diferent domainname to mapagent.fcgi.<BR><BR></FONT></DIV>
<P><FONT size=2>I'll weigh in here :)<BR><BR>There was a recent thread on the
ka-map list that is relevant to this <BR>discussion. The poster
claimed (I didn't verify it, but it seems <BR>correct) that tile sources
in google maps all point to a variety of <BR>server names
like:<BR><BR>m0.google.com<BR>m1.google.com<BR>m2.google.com<BR>m3.google.com<BR><BR>and
that each of these resolves to the same IP. This is being
done <BR>to provide more simultaneous connections than a default
configuration <BR>of a browser would make - and it works very
well.<BR><BR>The poster also provided a patch for ka-Map that implemented a
simple <BR>round-robin server picker from an array of available servers
for the <BR>tile code. He claimed substantial improvement in
apparent tile <BR>loading speed because more tiles loaded
simultaneously.<BR><BR>I am going to be implementing his patch in ka-Map (in a
slightly <BR>different way, but the same concept) because I need this for
a <BR>current client. I can report back on our success.<BR><BR>On a
side note, OpenLayers already has the capability to specify an <BR>array
of servers as a tile source for a layer.<BR><BR>Finally, we've been looking
closely at optimizing kaMap performance <BR>for our client. Part of
this has involved reorganizing how the tiles <BR>are physically cached on
disk to avoid problems with having too many <BR>entries per
directory. The other part was using the web server <BR>directly to
serve tiles. This means the client is aware of the <BR>server cache
structure and the cache is directly exposed through the <BR>web
server. A 404 error handler is used to trigger tile
generation <BR>when the cache does not contain a particular set of
tiles.<BR><BR>Also, we switched from Apache to lighttpd as it is quite a bit
faster <BR>at serving files. There are also other web servers that
are faster <BR>than Apache.<BR><BR>One of the problems I see with
MapGuide's tile caching mechanism is <BR>that the tiles are not stored at
the web tier, but rather at the <BR>server. This implies that you
must invoke some process in addition <BR>to the web server and wait for
the transfer between the server and <BR>the web tier, even if they are on
the same machine. This would be a <BR>very difficult problem to
solve in MapGuide, though, because the <BR>architecture allows you to set
up multiple web tiers and multiple <BR>servers in the back end - I don't
envy Bob this particular problem :)<BR><BR>Cheers<BR><BR>Paul<BR><BR>On
28-Feb-07, at 6:52 PM, Jason Birch wrote:<BR><BR>> Hi
Trevor,<BR>><BR>> There are two points here:<BR>><BR>> - If the
tiles were served directly from disk by apache (or IIS), you<BR>> will
likely better performance than through the tileservice, primarily<BR>>
because there will be less CPU overhead. However, the recent
changes<BR>> there (caching maps, etc).<BR>><BR>> - From the client
level, they only have two pipes to receive those <BR>> tiles<BR>>
through, so even if you're serving 100 tiles per second, the client is<BR>>
only going to be able to download two at a time. They have to
pull <BR>> down<BR>> all of the HTML and JS code through the same
pipes, so initial load <BR>> time<BR>> can be a killer at high
resolution (more tiles to fill the screen).<BR>><BR>> On a
somewhat-related note, TileCache looks interesting:<BR>> <A
href="http://labs.metacarta.com/wms-c/">http://labs.metacarta.com/wms-c/</A><BR>><BR>>
Jason<BR>><BR>><BR>> -----Original Message-----<BR>> From: Trevor
Wekel<BR>> Subject: RE: [mapguide-users] Guestion about speedup
mapguide,diferent<BR>> domainname to mapagent.fcgi.<BR>><BR>> I don't
know how much network latency and bandwidth affect tile <BR>>
serving<BR>> speeds. However, I have had very good tile serving
performance over a<BR>> LAN with recent builds of MapGuide. I have
seen tile serving <BR>> speeds in<BR>> excess of 100 tiles
per second over a gigabit ethernet link with <BR>> current<BR>>
hardware (Pentium D 820).<BR>><BR>> It would also be worthwhile to
monitor CPU usage on the server while<BR>> tiles are being served. I
suspect the bottleneck is CPU and not <BR>> network<BR>> latency or
bandwidth.<BR>> _______________________________________________<BR>>
mapguide-users mailing list<BR>> mapguide-users@lists.osgeo.org<BR>> <A
href="http://lists.osgeo.org/mailman/listinfo/mapguide-users">http://lists.osgeo.org/mailman/listinfo/mapguide-users</A><BR><BR>+-----------------------------------------------------------------+<BR>|Paul
Spencer
pspencer@dmsolutions.ca
|<BR>+-----------------------------------------------------------------+<BR>|Chief
Technology
Officer
|<BR>|DM Solutions Group
Inc
<A href="http://www.dmsolutions.ca/">http://www.dmsolutions.ca/</A>
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